Power output of this PSU

[motorollin]

I have one of these small PSUs. The spec says it is 12v @ 200W. If I have worked it out correctly, this equates to 16.6 amps (200W/12v). So how do I work out what current I need to put in to the 12v input to get this amount of current out? And can I just divide the output current by the current required by each component to work out whether it will be sufficient to power everything?

I did look at the manual and also the power simulator on the web site, but TBH I was none the wiser. I find all this stuff really confusing!

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moto

[Oliver]

You are trying to choose an appropriate 12V DC adapter to supply your PW-200-M, right? I had a quick look at the manual. The DC-DC converter is pretty efficient at high load currents, so you should be able to select a supply rated at just a bit over the power requirements of the euipment you are driving. If you use a supply rated at say 1.2 times your load demands, then that should give you a bit of headroom for current draw.

The device is probably a combined switch mode regulator, and charge pump for the negative voltage. These things are pretty efficient, though they can add electrical noise into a system. It's not usually a problem though (depending on what is driven, and the type of bypassing used).

[motorollin]

Oliver wrote:
You are trying to choose an appropriate 12V DC adapter to supply your PW-200-M, right? I had a quick look at the manual. The DC-DC converter is pretty efficient at high load currents, so you should be able to select a supply rated at just a bit over the power requirements of the euipment you are driving. If you use a supply rated at say 1.2 times your load demands, then that should give you a bit of headroom for current draw.

Excellent, thanks! Now I just need to work out the power requirements of an EFIKA, a Radeon 9250, a CF card, an IDE -> USB adapter and a CD-ROM :crazy:

Oliver wrote:
The device is probably a combined switch mode regulator, and charge pump for the negative voltage. These things are pretty efficient, though they can add electrical noise into a system. It's not usually a problem though (depending on what is driven, and the type of bypassing used).

I'll take your word for it ;-)

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moto

[Oliver]

motorollin wrote:
Now I just need to work out the power requirements of an EFIKA, a Radeon 9250, a CF card, an IDE -> USB adapter and a CD-ROM.

You could just play it safe, and use a 12V supply capable of driving the maximum load. Provided that your load does not exceed the max load for your DC-DC converter (I think this is unlikely), then you will have no problems.

You should keep in mind that your DC-DC converter efficiency is not so good under low loads. Because of this, if the converter is running on much less than max load, then you need to provide a greater excess of current beyond what is being delivered to your load, in order to supply the inefficiency of the converter.

I'm not sure, but I doubt you would save a lot of money by using a lower rated 12V supply anyway.

[motorollin]

Oliver wrote:
You could just play it safe, and use a 12V supply capable of driving the maximum load. Provided that your load does not exceed the max load for your DC-DC converter (I think this is unlikely), then you will have no problems.

Was my calculation above correct, making the maximum output 16.6A? If so, that would need an input of about 20A :-o

Oliver wrote:
You should keep in mind that your DC-DC converter efficiency is not so good under low loads. Because of this, if the converter is running on much less than max load, then you need to provide a greater excess of current beyond what is being delivered to your load, in order to supply the inefficiency of the converter.

So I might not need as much as 1.2* the required supply if I run it at maximum?

Oliver wrote:
I'm not sure, but I doubt you would save a lot of money by using a lower rated 12V supply anyway.

Well, I already have a 4.5A 12v supply so if I can get away with that then I have saved money by not having to buy a new one. And I suspect a supply powerful enough to run the PSU at full power would be expensive (and massive).

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moto

[Oliver]

Your calculation is right, and it is also true that you won't really need that much power. It is just an easy way to handle the calculations if you cover the worst case.

The reason I suggested a factor of 1.2, was that a lot of supplies don't really handle being driven close to their rated maximum.

Anyway, as you have a supply already, and you know what you will be driving, it would be worth looking a little closer.

I'll have a look into the requirements and get back to you.

[motorollin]

Cheers Oli! I'll do some Googling for the power requirements and see if I can work it out.

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moto

[bloodline]

I'd be genuinely surprised if a complete effica system required more than 60watts...

[motorollin]

You're probably right. But I don't want to overload it and risk damaging the PSU.

Like the new avatar BTW!

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moto

[bloodline]

motorollin wrote:
You're probably right. But I don't want to overload it and risk damaging the PSU.

I'll bet your existing supply will do the job just fine! If it doesn't I'll buy you a new one :-D
 

Like the new avatar BTW!

Hahahaha, Cheers! Just keeping my Avatar up to date :-)

Still no news yet on how the edit is going... I hope it turns out ok :crazy:

[motorollin]

bloodline wrote:
I'll bet your existing supply will do the job just fine! If it doesn't I'll buy you a new one :-D

Deal! I suppose I can just try it and quickly unplug it if it looks like it's not working...

bloodline wrote:
Still no news yet on how the edit is going... I hope it turns out ok :crazy:

I'm sure it will be great. I can't wait to see it!

[bloodline]

motorollin wrote:

bloodline wrote:
I'll bet your existing supply will do the job just fine! If it doesn't I'll buy you a new one :-D

Deal! I suppose I can just try it and quickly unplug it if it looks like it's not working...

I'll bet your MacBook doesn't draw more than 50Watts... and that's a much more powerful system with a display and battery!

bloodline wrote:
Still no news yet on how the edit is going... I hope it turns out ok :crazy:

I'm sure it will be great. I can't wait to see it!

Well, We've not been called back for reshoots, so I guess the director is happy with the footage!!!

[motorollin]

bloodline wrote:
I'll bet your MacBook doesn't draw more than 50Watts... and that's a much more powerful system with a display and battery!

Looks like you're right! I just cut off the plug from the IDE -> USB adapter's own PSU and wired it on to the 12v and GND lines on a molex extension. When I fired up the EFIKA with the adapter powered off of the PW-200-M's hard disk power connector it worked perfectly! What is even better is that my 4.5A 12v PSU which is feeding the PW-200-M fits nicely inside my lego case, meaning I can just have an IEC mains socket on the back :-D

bloodline wrote:
Well, We've not been called back for reshoots, so I guess the director is happy with the footage!!!

Like I said: Next stop Eastenders :-P

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moto

[bloodline]

motorollin wrote:

bloodline wrote:
I'll bet your MacBook doesn't draw more than 50Watts... and that's a much more powerful system with a display and battery!

Looks like you're right! I just cut off the plug from the IDE -> USB adapter's own PSU and wired it on to the 12v and GND lines on a molex extension. When I fired up the EFIKA with the adapter powered off of the PW-200-M's hard disk power connector it worked perfectly! What is even better is that my 4.5A 12v PSU which is feeding the PW-200-M fits nicely inside my lego case, meaning I can just have an IEC mains socket on the back :-D

Brilliant! :-)

Now, have some fun with it... I must dust off my old Mini-ITX board... it's not been used in a while... I've just been too busy :-(

bloodline wrote:
Well, We've not been called back for reshoots, so I guess the director is happy with the footage!!!

Like I said: Next stop Eastenders :-P

Hahaha, I was going to say my acting is probably too wooden... but actually, it's probably not wooden enough! :-D